1 files changed, 30 insertions, 0 deletions

diff --git a/src/test/ui/issues/issue-41936-variance-coerce-unsized-cycle.rs b/src/test/ui/issues/issue-41936-variance-coerce-unsized-cycle.rs
new file mode 100644
index 000000000..3d678ba04
--- /dev/null
+++ b/src/test/ui/issues/issue-41936-variance-coerce-unsized-cycle.rs
@@ -0,0 +1,30 @@
+// check-pass
+#![allow(dead_code)]
+// Regression test for #41936. The coerce-unsized trait check in
+// coherence was using subtyping, which triggered variance
+// computation, which failed because it required type info for fields
+// that had not (yet) been computed.
+
+#![feature(unsize)]
+#![feature(coerce_unsized)]
+
+use std::{marker,ops};
+
+// Change the array to a non-array, and error disappears
+// Adding a new field to the end keeps the error
+struct LogDataBuf([u8;8]);
+
+struct Aref<T: ?Sized>
+{
+    // Inner structure triggers the error, removing the inner removes the message.
+    ptr: Box<ArefInner<T>>,
+}
+impl<T: ?Sized + marker::Unsize<U>, U: ?Sized> ops::CoerceUnsized<Aref<U>> for Aref<T> {}
+
+struct ArefInner<T: ?Sized>
+{
+    // Even with this field commented out, the error is raised.
+    data: T,
+}
+
+fn main(){}